One of the clear themes that can be identified that link these two poems is the way that both of them are examples of "carpe diem" poems, or poems that focus on the imperative of seizing the day and making most of the opportunities for loving now rather than delaying such gratification for the future. Both feature a speaker who tries to tempt a female audience that life is so short that they should love them now in the present, because if they wait too long it will be too late. In "A Passionate Shepherd to His Love," for example, the speaker paints a beautiful pastoral vision of what his life will be like with the woman he is addressing in order to try and tempt her to join him:
Come live with me and be my love,
And we will all the pleasures prove
That valleys, groves, hills, and fields,
Woods, or steepy mountain yields.
The countryside seems to be an apt environment for the speaker and his lover to "prove" all kinds of different "pleasures," and the images he paints are persuasive in their beauty and charm.
Whilst "To His Coy Mistress" is a similar poem of a lover addressing a woman and urging her to be with him, the big difference is that this poem focuses far more on the dangers of tarrying and being "coy." Even though the speaker would love to spend ages courting her as her beauty demands, he is aware of how short a time they actually have:
But at my back I always hear
Time's wingèd chariot hurrying near;
And yonder all before us lie
Deserts of vast eternity.
He uses images of the grave as a "fine and private place," to highlight the need for urgency, as "none I think to their embrace." The key image of time as a chariot that is always "hurrying near" serves to try and persuade the audience that she must accept the speaker's advances now, in order to make the most of what little time they have. Both poems therefore can be linked through their status as "carpe diem" poems, but within that there is also room to explore how they differ in terms of the presentation of that "seize the day" approach to life.